Method of flotation



Patented Dec. 1, 1931 UNITED STATES PATENT OFF-ICE GEORGE G. THOMAS, F ELIZABETH, AND LUDWIGJ. CHRISTIAN, OF JERSEY CITY, NEW JERSEY, ASSIGNOBS TO AMERICAN CYANAMDJ COMPANY, 01' NEW YORK, 11'. Y,

A conrona'rlon or MAINE manner: or rno'ra'riou No Drawing. I

ores, more particularly to diflerential flota-' tion involving the use of a cyanide.

It has been well known for a number of 5 years that sodium cyanide and other soluble cyanides when added to a mill circuit containing complex ores to be floated, acts as a depressant of some of the minerals, while allowing flotation of others. nides are so used to a considerable extent in various types of ores, for example, ores containing copper and iron, where the cyanide inhibits the flotation of the iron allowing the copper to be removed as a concentrate.

The general procedure has been to provide a mill circuit of ore, for instance, a low grade copper iron ore, in a suitable dilution with water and to add a substantial,

amount of lime to the circuit to make the same definitely alkaline. Suitable flotation reagents were added to the circuit and flotation of the copper, for example, was effected, either with or without the use of a cyanide. The remainder, containing most of the iron in the ore, was subjected to another flotation operation in the presence of an acid such as sulphuric acid. I

In such a procedure, the lime was a considerable-expense as, for example, an ordinary ore from Eastern Canada required about pounds of lime per ton which, at say 1 cent'per pound, meant a cost of reagent of 10 cents per ton. j

In the second stage of the flotation it was necessary to add a large amount of sulphuric acid, say 30 pounds per ton, most of which was necessary to neutralize the lime originally added. This involved an expense of approximately 12' cents per ton. In a large operation, the cost of these reagents becomes very considerable.

We have found that contrary to the prior belief that a cyanide cannot be used in flotation circuits except in alkaline solutions, we operate in neutral or acid solutions with excellent results. By so doing we are enabled to entirely omit the addition of lime in most cases and in exceptional cases 50 where the acidity of the mill solution is very Application filed December 13, 1927. Serial No. 239,818.

high we reduce the lime to a very small amount. i

By reason of the elimination of most or all of the line in the first flotation operation, we then in the second stage, for the recovery of the iron, use only a very small amount of the acid such as sulphuric acid, thereby saving practically the entire cost of both lime and sulphuric acid. The amount of cyanide, for example, sodium cyanide,'necessary for the operation is very small being from .10 to .20 pounds of sodium cyanide per ton of ore at a cost of approximately 2 to 4 cents per ton of ore compared to the cost of alkali and acid of about 22 cents process.

As an example of the operation of our invention, we took the above mentioned ore from Eastern Canada which required to float the copper 10 pounds of lime per ton in addition to the ordinary flotation reagents. We ran a series of tests on this ore, usin no lime and adding small amounts of so ium cyanide in place thereof, together with Aerofloat #25 and pine oil as the flotation reagents. Aerofloat is the flotation reagent de-. scribed and claimed in the patent to Whitworth #1,593,232, dated July 20, 1926. o

The pH or hydrogen ion concentration of the mill solution was 6.8 to 7.0 which 1s a practicallyl neutral solution. The results of the test s owed that by the elimination of the lime and the additionof a small amount per ton by the old l of sodium cyanide, the results obtained were at least as good as those obtained with'the use of 10 pounds of lime per ton as shown by the following table:

Mill run reagents: lime 10.0%, T 6: T mixture 0.163, pine oil, 0.022}, 1 and xanthate 0.023;.

very small amounts giving the following results in a circuit having a pH of.5.2 to 5.4.

Reagents Fe conlbs/ton centrate T Recovery Test H so 53? Cu per Fe per Cu per Fe per Cu per Fe per cent cent cent cent cent cent Mill run 0. 34 44. 0 0. 27 6.6 Not 'iven 1 2. 0 0. 35 45. 2 0. 09 5. 9 5. 4 70. 4 2 3. 0 0. 08 9. 47. 5 0. 08 3. 1 9. 4 85. 1 3 3. 0 0. 08 0. 46. 6 0. 08 4. 6 11. 2 82. 5

Mill run reagents: 11:30; 29.0% coal tarcreosote 0.945;, xanthate 0.06# and pine oil 0.03#.

It will be seen that the recoveries were as good as had been previously obtained with very large amounts of sulphuric acid.

Another orev from one of the Southwestern States was tested in-a similar manner, comparing the results obtained with'the use of small amounts of sodium cyanide in a definitely acid solution with results obtained by-the use of lime in a definitely alkaline solution. The following table, denoting the copper flotation or recovery, shows that the cyanide flotation is superior to the lime flotatlon. The results show both better recoverles and lower tails.

Reagents Concentrate Fe lbs/ton assay Tall Cu elim- Aeroassay r'eeovina- Test float Cu ery tfon pH #15 Cu Fe per per per NaON 0210 per per cent cent cent 1 cent cent 1------ None. None 0.115 18.45 15.8 0.1 4 78. 1 5.5.06l2-6.4 2 0. 10 N one 0. 115 18. 95 15. 9 0. 13 89. 4 53. 5 6. 2-6. 4 3 0.2) None 0.115 18.30 16.0 0.11 90.4 52.96. 2-6.4 4 None. 2. 0 0. 115 20. 95 18. 3 0. 18 83. 9 64. 9 8. 6-8. 8 5 None. 4. 0 0. 115 21. 25 19. 4 0. 14 87. 5 52. 8 9. 8 6 None. 6. 0 0. 115 21. 80 18. 9 0. 14 87. 5 54. 3 "I. 9. 8 "a From the above examples of our invention 7 it will be clear that we have discovered the important fact that a cyanide in very small amounts can be used to replace lime in the differential flotation of ores, where the circuits are neutral or acid, and that in circuits which had previously employed a cyanide in alkaline solution, most or all of the lime may be omitted.

, Previously, cyanide when used in flotation had been used only in alkaline circuits with the addition of lime in large amounts and the results obtained were not markedly supe-, rior to those obtained by the present inven tion'. This invention allows of a very large and considerable saving in cost of reagents ores under varied gether with the very material savin in cost of reagents. Our invention is, there ore, not limited to the specific examples set forth above, but includes various procedures involving the use of sodium or other soluble cya-nides in flotation circuits, of neutral or acid character as set forth in the claims pended hereto.

What we claim is: 1. In the concentration of ores, the step of subjecting the ores to froth flotation in an acid medium and in the presence of a single base cyanide.

2. In the concentration of ores, the step of subjectingthe ores to froth flotation in an acid medium and in the presence of a single base cyanide in amount not exceeding 1b. of cyanide per ton of ore.

In testimony whereof, we have hereunto subscribed our names this 6th day of December, 1927.

GEORGE G. THOMAS. LUDWIG J. CHRISTMANN. 

